The objective of the proposed research is to produce, purify and characterize all of the substances that are important in the pathogenesis of Pseudomonas aeruginosa in order to evaluate their roles. Studies on the exotoxins produced by the organisms are the central part of the objectives but our interests also include the phospholipase and the erythrogenic toxins. Studies on the exotoxins are directed to the mass production, purification and toxoid formation of exotoxin A for the purpose of active immunization as well as the production of antitoxic sera. There are exotoxins that are serologically distinct from the exotoxin A and their studies will be included. Phospholipase C produced by P. aeruginosa will be evaluated primarily for its role in the destruction of the surfactant on the alveolar surface of the lungs as well as the lung tissue itself. The erythrogenic toxin will be studied to evaluate its roles in the pathogenesis and to examine its possible identity with the permeability factor or the enterotoxin. This laboratory is engaged in an international effort to establish a serotyping schema of P. aeruginosa that can be used as the international standard. The study includes the evaluation of standard serotypes from various serotyping schemata, production of antisera and their pools, and evaluations of the new typing sera by many laboratories in this country and abroad.